This invention relates to a weapon system utilizing a line of sight guidance system in a beamrider missile, and in particular, to a system carried by the missile for obtaining missile roll position data. While the invention is described in particular detail with respect to a weapon system and missile control use, those skilled in the art will recognize the wider applicability of the inventive concepts disclosed hereinafter.
The prior art reveals a number of missile systems utilizing a missile launched into a projected beam, the missile flying along the line of sight of the beam to an intended target. One particular prior art device with which the invention disclosed hereinafter is useful is disclosed in a U.S. Pat. by Andrew T. Esker et al, No. 4,014,482, issued Mar. 29, 1977. The control system disclosed in Esker et al in turn is compatible with a missile disclosed in a U.S. Pat. to Tucker, No. 3,868,833, issued Mar. 4, 1975. The missile disclosed in the Tucker patent includes thruster elements, the firing rate and firing direction of which are controlled to position the missile. Esker et al, U.S. Pat. No. 4,014,482, discloses a line of sight guidance system in which the radiated output of a pulsed laser is spacially modulated to produce a beam radiated from an optical projector. The radiated beam contains all informational parameters required to enable a missile launched into the beam to determine its position with respect to beam center. Esker et al may be used in conjunction with the Tucker missile and offers certain operational improvements over the missile control system described in Tucker. Esker et al, U.S. Pat. No. 4,014,482, and Tucker, U.S. Pat. No. 3,868,833 are intended to be incorporated by reference herein.
In the Tucker and Esker et al patents, the missile configurations disclosed employ a conventional inertially stabilized position gyro for determining the roll position of the missile. While such gyros work for their intended purpose, they are handicapped because the mechanical designs of the gyros require limitations on the acceleration rates of the missile. Generally, the acceleration limitation is below one thousand g's (standard acceleration of gravity unit). High launch accelerations, i.e., over one thousand g's are desirable in order to reduce the time of missile flight to the target and thereby reduce the time period in which the gunner is susceptible to counter fire from the intended target.
As disclosed hereinafter, the missile of this invention is provided with a pair of optical receivers. The optical receivers are located on the missile a fixed distance apart, facing a beam projector at the launch site. Signals obtained from the first receiver are processed as disclosed in the above-referenced Esker et al patent, U.S. Pat. No. 4,014,482, for deriving the displacement error of the missile with respect to the beam center. The signal from the second receiver is used, together with the phase angle reference obtained in deriving the missile displacement error from beam center, in determining roll displacement error. The displacement errors from each axis are added and divided by two. The resulting error is then processed through a stabilization network and is utilized to develop missile roll angle reference in the form of two ramp voltages, each representing 360.degree. of missile roll angle separated in phase by 180.degree..
The prior art reveals a number of guidance systems including those which utilize dual radiation detectors from a single radiated beam source, as for example, described in U.S. Pat. to Ede, No. 3,557,372. The Ede patent, while working for its intended purpose, provides relatively low quality information unsuitable for precision control applications, required, for example, by the missile applications discussed in conjunction with this invention.
One of the objects of this invention is to provide a low cost means for determining roll position error in a guided object.
Another object of this invention is to provide system means for determining roll position error electronically.
Yet another object of this invention is to provide a missile system in which the roll position sensor in the missile is capable of withstanding acceleration forces in excess of one thousand g's.
Another object of this invention is to give roll position information and derived roll rate information to a guidance system in the form of pulses contained in the guidance beam, the sensitivity of the roll position information being essentially independent of the amplitude of the received pulses.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.